added docs about array attributes to the guide

docs/guide/bootstrap-widgets.md

@@ -3,7 +3,9 @@ Bootstrap Widgets
 
 > Note: This chapter is under development.
 
-Out of the box, Yii includes support for the [Bootstrap 3](http://getbootstrap.com/) markup and components framework (also known as "Twitter Bootstrap"). Bootstrap is an excellent, responsive framework that can greatly speed up the client-side of your development process.
+Out of the box, Yii includes support for the [Bootstrap 3](http://getbootstrap.com/) markup and components framework
+(also known as "Twitter Bootstrap"). Bootstrap is an excellent, responsive framework that can greatly speed up the
+client-side of your development process.
 
 The core of Bootstrap is represented by two parts:
 

docs/guide/input-forms.md

@@ -59,7 +59,7 @@ class LoginForm extends Model
 }
 ```
 
-The controller will pass an instance of that model to the view, wherein the Active Form widget is used:
+The controller will pass an instance of that model to the view, wherein the [[yii\widgets\ActiveForm|ActiveForm]] widget is used:
 
 ```php
 use yii\helpers\Html;
@@ -108,6 +108,18 @@ If you want to use one of HTML5 fields you may specify input type directly like
 <?= $form->field($model, 'email')->input('email') ?>
 ```
 
+Specifying attribute of the model can be does in more sophisticated ways for example when an attribute may
+take an array value when uploading multiple files or selecting multiple items you may specify it by appending `[]`
+to the attribute name:
+
+```php
+// allow multiple files to be uploaded:
+echo $form->field($model, 'uploadFile[]')->fileInput('multiple'=>'multiple');
+
+// allow multiple items to be checked:
+echo $form->field($model, 'items[]')->checkboxList(['a' => 'Item A', 'b' => 'Item B', 'c' => 'Item C']);
+```
+
 > **Tip**: in order to style required fields with asterisk you can use the following CSS:
 >
 ```css